1. Field of the Invention
The present invention is directed to a lockout mechanism for a fastener driving tool used to install fasteners in a substrate, for example in an overhead application.
2. Description of the Related Art
A variety of different fastening driving tools exist for driving fasteners into numerous substrates, including tools used to install fasteners in situations where a significant separation between the user and the muzzle of the tool exists such as when a user wants to drive a fastener into a ceiling substrate. In these situations, fasteners may be loaded individually into the muzzle end of the tool while charges to drive the fasteners may be fed into the tool at a position behind a piston. Combustion of a charge causes the piston to be driven forward, thereby driving the fastener forward and into the substrate.
Due to the separation that may exist between the user and the muzzle of the tool, several tools employ an apparatus for extending the user's reach and for firing the tool. Oftentimes, tools with these extensions are fired by compressing the tool against the substrate or work surface and then providing a secondary compressive force to the entire apparatus to cause the tool to fire.
One drawback of tools operating in this fashion is the possibility of inadvertent actuation or misfiring. Applying too much pressure initially may cause the tool to actuate prematurely, which may cause the fastener to be driven in an undesired location or orientation. Alternatively, this pressure may cause the firing sequence to occur out of order, for example, causing the firing pin to release without sufficient force to combust a cartridge, resulting in a misfire of the tool.
One solution to this problem is described in U.S. Pat. No. 7,896,210, titled “Fastener Actuation System,” and which was invented by two of the inventors named here. The '210 patent describes a system including a tool and a pole assembly couplable to the tool. The pole assembly includes a lockout mechanism that prevents the tool from firing when the tool is oriented generally below a horizontal level. While this lockout mechanism is successful at preventing unintended firing of the tool, it adds additional weight to the pole assembly. In addition, the tool still may be subject to misfiring if the pole assembly is not attached.
What is needed is a fastener actuation system that overcomes the drawbacks described above.